The major research project is a prospective cohort study of 600 elderly patients admitted to the general medical and surgical wards at Yale-New Haven Hospital, designed to evaluate the incidence, predictors, and adverse outcomes of delirium. The study will focus on identifying iatrogenic or hospital-related factors which may be amenable to intervention. Predictors and new episodes of delirium will be ascertained by daily patient and nurse interviews from admission until discharge, supplemented by medical record reviews. Follow-up interviews will be done at 3 and 12 months after discharge, to evaluate long-term outcomes associated with delirium (e.g., functional and cognitive decline, mortality). This will be the first prospective study of delirium which uses a standardized, validated diagnostic tool to identify delirium. In addition, the focus on incident cases of delirium due to iatrogenic or hospital-related factors is unique, and will be particularly valuable in designing future intervention trials. Future research plans include a substudy on the proposed cohort to examine pathophysiologic changes in delirium --- specifically abnormalities in cerebral blood flow and metabolic activity with single photon emission computed tomography (SPECT) during and after delirium. In addition, a randomized, controlled intervention trial to prevent delirium is planned based on the results of the proposed project. Finally, collaborative studies will be carried out with the MacArthur Research Project on Successful Aging, including analyses of data pertaining to cognitive functioning in their 1,350 subjects. One study will examine psychosocial and biomedical factors associated with high cognitive functioning in this group.